Shared Space
by AThingHappenedOnce
Summary: The Host AU- The Earth has been overtaken by an alien race of parasites. Castiel is given the task of finding out where remaining resistance is via captive Dean Winchester, but what happens when Castiel sympathizes with the humans? Destiel, Rated T for Dean. (swearing etc.)
1. Chapter 1

In a room that had the look of a hospital morgue, three figures, silent, two in black and one in white were standing around a man with dirty blond hair covered in cuts and bruises of a variety of colours ranging from yellow to brown and black. One of the people in black clothing; a doctor, spoke:

„Barely a bone not broken, or organ ruptured. I cannot tell you why he is not dead. "

Shifting her eyes between the man who spoke and the one on the table, she replied:

„This one wants to live".

Taking that as his cue, the doctor grabbed a metal rectangle-shaped medicine pod whilst gently opening the blonde's mouth. He held the pod pointed, a short distance away from the opened mouth, squeezing the button on the other end. As the pod released its gaseous content, the wounds started to disappear, revealing clean skin. Next, the doctor turned the man's head so it was facing away from him, revealing the back of his neck. As he made a shallow incision close to the spine, the other darkly dressed man, the doctor's assistant, took an oddly shaped piece of metal out of a small crate. Gently, the assistant moved the container onto a shiny metal table, cradling it in his hands as he did so. The container opened, revealing a caterpillar-like creature with a bountiful number of slender tentacles, a soul. The doctor picked it up with great care and transported it to the cut he had made moments prior. The soul slowly moved into the body, moving towards the brain at a low pace. Connecting to it, the parasite took control over the physical form. He opened his eyes, the previously green eyes' pupils were surrounded by a forest of neon blues, now resembling those of everyone else in the room. The new inhabitant looked around, taking in his environment, a blank expression on his face.

"Welcome", said the doctor, "I am Uriel, what shall I call you? You have lived many lives on many worlds. A wanderer such as yourself, there must have been a name."

The woman was pacing around the room slowly, observing the exchange.

The soul, still getting used to his new vessel, replied to Uriel:

"Call. Me. Castiel."

Uriel gave Castiel a ghost of a smile, content evident in his features.

"When will he be able to work?"

"Not now."

A hint of embarrassment was visible on the woman's face upon replying:

"Of course."

**A/N: As this is my first attempt at fanfiction, feel free to point out any flaws. Seriously, you can be as harsh as you want. A thank you and shoutout goes out to my beta Teddy (deandeservestobeloved on tumblr)**


	2. Chapter 2

_He was hiding. He had to protect him. They were going to hurt him. He looked over his shoulders, backed up behind a corner, leading them away was his top priority. He started running toward another hallway when he was ambushed by a group of what the few remaining unoccupied humans call "angels". _

_"__Please, come with us" "We don't want to hurt you." "Please don't hurt yourself."_

_They wanted to take him. They were going to take away one of the only things he had left in his defiantly miserable life, his freedom. He knew exactly what he should do. The only thing that still could be done. He hit one of the angels in the face with a steel pipe he had found earlier. Repeating the action with another two, he raced up the stairs behind him. He knew they were following close behind. He wanted them to see this. Using the hallway he found himself in as a ramp, he ran as fast as he could towards the window at its end. As he jumped out, instinctively covering his face and neck with his hands, he crashed through the window, the angels watching him. As he was falling, his last thoughts were dedicated to the ones he protected, at peace with his destination, death. Suddenly, everything went to black._

* * *

Castiel awoke with an inorganic finality. Knowing that it was unlikely for him to go back to sleep after witnessing that memory, he slowly rose out of his bed. His bare feet touched the floor gently, he still wasn't used to the sensations that his new vessel had brought him. He walked towards the bathroom of his assigned living quarters. Now in front of the mirror, he stared at the unfamiliar face that looked back at him. A young man, maybe in his mid-twenties. A ghost of a stubble on his lower face, while the bridge of his nose and top of his cheeks were lined with freckles. Castiel lifted his hands up to his face to feel his new features when he was interrupted by the awakening of another presence in his mind.

_No. I didn't die, bitch. _A rough voice echoed in Castiel's mind; _That's right. I'm not dead. This body ain't yours. It's mine._

Castiel looked into the eyes of his vessel in the mirror.

"No. Mine."

"Mine," he repeated, not just for the voice inside his head, but to himself, justifying his take-over.

* * *

**A/N: Thank you for the follows and favourites ^u^ And a special thank you to SmileBecauseYourBeautiful. I'll post the first few chapters every two or three days, and then about once a week. Again, please review, telling be what I do wrong helps me get better**


	3. Chapter 3

**A/N: thank you so much for the follows. you all deserve millions of flowers and cute weevils :3 note: ****_italics are probably going to be exclusive for dean so there's no confusion in the future_ **

* * *

The next morning, Castiel was taken into a small, yet somehow spacious room. A window consumed one of the walls. It contained only a table and a chair.

"I don't know how much you know about this new world. Almost every human has been successfully occupied. As with the other planets we've inhabited, we did not change this world, but experienced it. Perfected. " The woman from the day before, Naomi, started.

_What? You thought I'd give up just like that? _The voice spoke again.

"However. There are still pockets of human resistance, your host is one of those resistances."

Castiel understood. "You want me to locate his memories?" He moved the chair back, going on to sit.

"Yes. From those memories we can locate other rebels."

_Good luck with that._ The voice added.

"Most humans fade away, but there are a few who fight the occupation."

_Damn straight. _

But although he could vocalize his thoughts, the man could not suppress most of his memories.

"His name is Dean Winchester, he was born in Lawrence, Kansas. His family escaped the initial waves of colonization. But it was only a matter of time before they were discovered. His father was found in an abandoned hospital. He took his life rather than be taken by our seekers and saved the lives of his children. Dean has been on the run ever since with-"

_No! Don't you dare say his name!_

Castiel stopped for a moment, strangely unsure whether to say the name or not. But, the moment of doubt was quickly overpowered.

"-Sammy. Sammy is Dean's brother, Sam Winchester."

_Damn it._


	4. Chapter 4

**A/N: sorry for the short chapter.. and not uploading. i honestly have no excuse, as i am stupendously lazy. we're also going into one upload a week territory... anyways, enjoy and sorry**

* * *

Later that day, Castiel was walking around the city he now inhabited. The streets were not crowded; cars drove at a low speed, and the houses he passed in perfect condition. Lawns were kept neatly and there was no uniqueness in the people walking by. A perfect harmony of a society without difference.

"I understand why you were resisting earlier. But think of the greater good.-" Castiel began.

_Call it whatever the hell you want, this is murder. You ain't just takin' bodies. There are people in there!_

Castiel did not know how to address that, Dean had made a point, did his people really have the right to overtake sentient creatures?

The rest of the walk was silent.

* * *

When Castiel came back into his living quarters, he spoke up about something that had been bothering him during the silence of the walk:

"Why would you be angered by Naomi's knowledge of your brother's name? It is no strategical advantage for the seekers to know."

_It just sounds so wrong coming from you._

"I don't understand."

_I'm just angry, okay? I should have died. I should've died protecting Sammy, not be stuck in my own fucking head with some alien creep controlling me!_

Dean did not know why he was telling Castiel all this, he rationalized it to not being able to lie in his own head.

That night Castiel dreamt of another one of Deans memories.

* * *

**A/N: sorry again.**


	5. Chapter 5

**A/N: thank you for the follows and favourites, it really means a lot :3 so this chapter is the longest so far, as i had an epiphany at one point in the last week. a shout-out goes to a horizon that borders the sea and airy distance to allow me to plot out the next few chapters**

**anyway, enjoy**

**(note: "_italics in quotation marks (that isn't in the nightmare,__ obviously_**_)_**_ means independent thought that is not heard by the other_")**

* * *

_It was late and Dean had to go sleep. His dad was back from work already, and that meant he hadn't gone out drinking, which was a relief. His mum was getting Sammy into bed. He put on his nightie and strode down the hallway to Sam's room to kiss his little brother goodnight. He did so, after the approval of his mother, of course. He went to bed himself right afterwards.  
The first thing he remembered after waking up was the stench of smoke. Dean immediately got out of bed and into the hallway. He was met by his father, John Winchester, cradling his six-month-old brother in his arms. John handed Dean the baby carefully, yet swiftly.  
"Get your brother out as fast as you can." Dean wanted to ensure the safety of his mother but John quickly added: "Now, Dean. Go!"  
Dean obeyed and made his way down the stairs, running out of the house. He turned around to see their home slowly being consumed by flames and becoming a husk of what it once was. Eaten away by the raging fire. A fate Dean's father would also suffer. After a few moments of staring, Dean was grabbed around the waist by John, who then got them away from the burning building without a second glance.  
The Lawrence fire department arrived only a few minutes later. They gave the three Winchesters blankets, and were later seen carrying a black body bag out of the then freshly extinguished building. When Dean looked at his father's eyes for comfort, all he saw was the darkness that had slowly started to loom in them._

* * *

Dean was freaking out. Where was Sam? Why couldn't he move?

"Sam!" Dean half-shouted in a tone that leaned toward a question.

Castiel was confused, as he was not the one who spoke aloud. He felt the pure emotion surging through him. A few moments later he was conscious enough to understand what was going on.

"Dean." Castiel said in a firm tone, "Dean, calm down."

No use. He tries again:

"You were having a nightmare. There is no immediate danger. You are safe."

That was when the last two days came back to him. Dean's breathing slowed down.

* * *

Castiel was in no position to go back to sleep. His mind was too busy processing those several past moments. How was Dean able to speak using his body? "_He seems to be able to gain partial control over parts of his body in cases of extreme determination or emotion."_ He reasoned. He continued his thought process with the nightmare:

_ "__It was so vivid. A memory? Both? What happened after the fire? How did Dean's father cope with taking care of an infant and young child?"_

* * *

Dean also had some thoughts that needed clearing:

_"__All this wouldn't've happened if I had only been more careful about checking for angels. I failed mom. I failed dad. I failed Sammy, and now I couldn't even die properly. I had one job and I couldn't even do that. God knows if Sam made it to Bobby's."_

He could feel his pulse rising and so stopped himself from thinking further into that particular issue; he didn't want Castiel to worry. _"Did I seriously just bother myself with that?"_ Dean tried not to think about him either. Finding nothing else to regard, nor the will to sleep, he stared at what Castiel seemed to be staring at: the ceiling.

* * *

Castiel, after about half an hour of incessant silence and a build-up of untameable curiosity, concluded that Dean wasn't going to engage in conversation, so he took the liberty of doing it himself:

"Do you intend to talk about it?"

_So you can report it to Ms. I've-got-a-broom-up-my-ass? No thank you._

"I believe her name is Naomi, but I'm presuming that was a figure of speech."

_No shit._

"She probably couldn't. Though it would be an impressive feat."

Dean couldn't help but chuckle, as Castiel couldn't help but smile slightly. After a few moments Castiel resumed:

"Once again; how could my concern for your well-being and overall knowledge of your unimmediate past be of any use for the Seekers?"

Silence.

"Do you intend to reply?"

_I don't want to talk about it._

He didn't push the matter any further. Having relieved some tension, both were ready to slip out of consciousness.


	6. Chapter 6

**A/N: sorry for the late chapter. once more, i have no excuse but my laziness, now augmented with writer's block. another shout-out to my amazing beta teddy (deandeservestobeloved on tumblr) and thanks for the follows and favourites**

* * *

When Castiel awakened, they took him to the same room as the day before. Naomi was sitting at the table. This time, a chair was on the opposite side of it. The professionally dressed woman gestured towards the chair, encouraging Castiel to settle on it. Her posture was stiff as before, and her movements seemed meticulously planned.

"She might be a _bit_ uptight…" Castiel mumbled, his eyes inspecting the floor as he headed toward his designated seat.

Dean, who had been surprisingly quiet up to that point, chuckled and added:

_And the Earth might be round.*_

Castiel twitched the edges of his vessel's lips up ever so slightly, only to drop them back down a mere second later.

"Did you say something?" Naomi's voice broke him out of his and Dean's little exchange.

"I did not. I apologize." Castiel replied, with a hint of absentmindedness.

He seated himself, and rested his hands on the table, intertwining his fingers in a prayer-like position. The moment he looked at the Seeker, she immediately asked:

"Do you have any new information?"

"I have no useful information."

"But you _have _information?"

"It is of no import."

"I must ask you to share it anyways."

Castiel looked down at the table, as if waiting for permission. Dean stayed silent. If he had control over a physical form, his eyebrow would be raised. He couldn't help himself from being curious about what seemed like Castiel _actually_ respecting his privacy.

"Well?"

Dean sighed and added a "Fine."

Castiel, after hesitating slightly, spoke:

"His mother died in a house fire when he was young."

He formed a mournful expression, which forcefully melted away after re-initiating eye-contact with Naomi. If he was caught sympathizing with Dean, he would surely be moved into another vessel, if not worse.

"Indeed. We have no use for this fact." Naomi concluded. "You are dismissed."

* * *

**_*don't worry. I know. It will be corrected_**

**_2. A/N: i hope you enjoyed this little semi-filler ^u^ there'll some more exquisite plot development soon, so stay tuned_**


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